An active vibration noise control apparatus (Active Noise Control Apparatus) that uses an adaptive notch filter (Adaptive Notch Filter) is known as a device that reduces vibration noise generated by a rotary machine such as an engine. Here, the vibration noise indicates vibration or noise generated by operation of a machine or the like. This active vibration noise control apparatus sets a frequency of the vibration noise identified from a rotation period of the rotary machine as a control frequency, generates a control signal in antiphase to the vibration noise of the control frequency, and outputs this as a secondary vibration noise, thereby reducing the vibration noise by interference between the vibration noise and the secondary vibration noise.
In this case, there arises a problem in which an effect of reducing the vibration noise becomes smaller when a difference is generated between a frequency of actual vibration noise and a control frequency, due to influence of an error in measurement by a period sensor that detects the rotation period of the rotary machine, a delay of a signal that reports a measurement value from the period sensor, or the like. To cope with this problem, there is proposed a method (patent reference 1) that corrects the control frequency according to change of an argument when a filter coefficient of the adaptive notch filter is expressed on a complex plane as a real part and an imaginary part of a complex number, and there is proposed a method (patent reference 2) that corrects the control frequency on the basis of the control signal on the basis of a difference between a frequency of the control signal after updating a filter coefficient obtained by the adaptive notch filter and the control frequency.